This invention relates to electrically illuminated push buttons and indicators which are used for example to indicate that a switch or an electrical circuit is in the `on` position or that some piece of electrical or other apparatus is operating.
If such devices incorporating a filament bulb are used in semi-hazardous surroundings, such as for example on the delivery pumps at petrol filling stations, precautions have to be taken to prevent a fire or an explosion in the event of a spark due to a lamp failure. The present invention provides an illuminated push button or indicator which can safely be used in semi-hazardous surroundings and in which the illuminating bulb can readily be replaced in the event of failure.
According to the present invention there is provided an illuminated push button or indicator comprising a housing having a lamp holder at one end thereof, said lamp holder having a first, tubular sleeve member extending therefrom to enclose a lamp connected to the lamp holder and a member detachably mounted on the other end of said housing provided with a translucent portion illuminable by said lamp, said detachably mounted member being slidable with respect to said lamp holder by means of a second tubular sleeve member which fits over said first sleeve and is axially slidable thereon.
The invention also provides a push-button operated illuminated switch comprising an elongated housing containing a lamp holder at one end thereof, said lamp holder having a first tubular sleeve member extending therefrom and enclosing a lamp connected to said lamp holder, the other end of said housing being closed by a plunger member having a first portion one end of which is provided with a translucent portion and from the other end of which extends a second tubular sleeve member which surrounds and is axially slidable on said first tubular sleeve member, said plunger member being slidable within said housing, said plunger having a longitudinally extending resilient arm extending inside said housing and the free end of which is provided with a catch member releasably engageable with an abutment on said housing, said plunger member including a second portion slidable within said housing and disposed between the first portion of the plunger member and the lamp holder and being urged towards said first portion by spring means, said second portion of the plunger means having a spring biassed member extending out of said housing to operate a switch mounted outside the housing and adjacent to said lamp holder.